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12th Physics weekly Test - 3 ( Electromagnetic Induction And Alternating Current )

St. Britto Hr. Sec. School - Madurai

12th Physics weekly Test - 3 ( Electromagnetic Induction And Alternating Current )-Aug 2020

Time : 1.00 Hours

Part - A

Multiple Choice Question - Answer All Question

A power of 11,000 W is transmitted at 220 V. The current through line wires is

50 A
5 A
500 A
0.5 A

The unit of self inductance is

Henry
Ampere
Farad
Ohm

Copper loss is energy loss in the form of _______

light
heat
sound
hysteresis

If a secondary coil has 40 turns, and a primary coil with 20 turns is charged with 50V of potential difference, then potential difference in secondary would be

50 V
25 V
60 V
100 V

In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is

\(\frac{Q}{2}\)
\(\frac{Q}{\sqrt3}\)
\(\frac{Q}{\sqrt2}\)
Q

The self-inductance Lof a solenoid is given as

\(L=\frac { { \mu }_{ o }NA }{ l } \)
\(L=\frac { { \mu }_{ o }{ NA }^{ 2 } }{ l } \)
\(L=\frac { { \mu }_{ o }{ N }^{ 2 }A }{ l } \)
\(L=\frac { { { \mu }_{ o }A } }{ Nl } \)

For an ideal transformer __________

E_pI_p = E_sI_s
E_pE_s = I_p
E_pE_s= I_s
I_pI_s = E_sI_s

In a LCR series a.c, circuit, the phase difference between current and voltage is 60°. If the net reactance of the circuit is 17.32Ω, the value of the resistance is

30Ω
17.32 Ω
10 Ω
1.732 Ω

\(\frac{20}{\pi^2}H\)inductor is connected to a capacitor of capacitance C. The value of C in order to impart maximum power at 50 Hz is

50 μF
0.5 μF
500 μF
5 μF

In a transformer, the number of turns in the primary and the secondary are 410 and 1230 respectively. If the current in primary is 6A, then that in the secondary coil is

2 A
18 A
12 A
1 A

A transformer

converts energy
changes voltage
changes current
changes both current and voltage

In a series RL circuit, the resistance and inductive reactance are the same. Then the phase difference between the voltage and current in the circuit is

\(\frac{\pi}{4}\)
\(\frac{\pi}{2}\)
\(\frac{\pi}{6}\)
zero

In electric power transmission, the wastage of power is

more at high voltages
independent of voltage
more at low voltage
low at low voltages

An alternator produces voltage waves equal to the number of _____________ used.

slip rings
windings
magnetsbrushes
brushes

The self-inductance of a straight conductor is

zero
infinity
very large
very small

In an a. c. dynamo, the induced current is _________ in nature.

alternating
increasing
decreasing
constant

Which of the following cannot be stepped up in a transformer?

input current
input voltage
input power
all

The instantaneous current in an AC circuit containing a pure inductor is i = I_o sinωt, The instantaneous emf is: The

e = E_osin\(\left( \omega t+\frac { \pi }{ 2 } \right) \)
e = E_osin\(\left( \omega t-\frac { \pi }{ 2 } \right) \)
e=E_osin(ωt - π)
e = E_osin

The property of a coil which enables to produce an opposite induced emf in it when the current in the coil changes is called _______________

electromagnetism
self - induction
mutual induction
parallel- induction

The voltage drop across the resistor in a LCR series circuit is __________________

V_R = IR
V_R = IR₂
V_R = I/R
V_R=R/I

An emf of 12V is induced when the current in the coil changes at the rate of 40 A S^-1. The coefficient of self induction of the coil is

0.3 H
0.003 H
30 H
4.8 H

The unit henry can also be written as

VS A^-1
Wb A^-1
Ωs
all

The necessary magnetic field for a low power a.c generator is produced by _________

electric coil
permanent magnets
electromagnets
batteries

The quantity that changes with time in an A.C current is

magnitude
direction
both magnitude and direction
none

The average power consumed per cycle is:

Zero
2000 W
1000 W
500 W

AC generator works on the principle of

self induction
mutual induction
electromagnetic induction
none of these

__________ principle is used in transformer.

mutual induction
electromagnetic induction
self induction
eddy currents

In RLC series AC circuit at resonance:

Resistance is zero
Net reactance is zero
impedance is maximum
voltage leads the current by a phase angle \(\frac{ㅠ}{2}\)

An inductor 20 mH, a capacitor 50 μF and a resistor 40 Ω are connected in series across a source of emf v = 10 sin 340 t. The power loss in AC circuit is

0.76 W
0.89 W
0.46 W
0.67 W

An emf of 12V is induced when the current in the coil changes at the rate of 40 A S^-1. The coefficient of self induction of the coil is

0.3 H
0.003 H
30 H
4.8 H

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